And this year Americans again voted on various Propositions. 10? states all voted to ban same-sex marriages, but as a friend pointed out, the wording of some of them seems to also ban defacto relationships too...

For example, Kentucky Amendment 1: Same-Sex Marriage voted in favour by 75% of voters says:

Amend the Kentucky Constitution "to provide that only a marriage between one man and one woman shall be a marriage in Kentucky, and that a legal status identical to or similar to marriage for unmarried individuals shall not be valid or recognized?"

Although... it seems the idea of a defacto marriage is dying in the US anyway *:

One other form of marriage has existed and continues to exist in some states. Common law marriage recognizes a de facto state of marriage when there has been no actual ceremony in a religious or civil setting. Common law marriage is marriage for all civil purposes, but it has a "waiting period." In a common law marriage, a couple is assumed to be married if they have lived together for a certain period of time. The concept of common law marriage is mostly historical - most states no longer recognize new common law marriages, and the number of those that do is dwindling.

* note I haven't looked very hard at that link, it may be run by crazy nuts. It was the first I found with Google.